This invention relates in general to monitoring fluid flow in a flow conduit system, and more particularly to detecting abnormal flow conditions such as leaks or catastrophic conditions such as plumbing failures in a fluid supply system.
Common flow conduit systems in wide use today include, for example, water supply systems for dwellings or other type buildings. With the important emphasis on conservation which exists today, it is essential to protect against water waste due to conditions such as leaks or plumbing failures in a water supply system. Such conditions not only result in wasting of a valuable natural resource but can cause serious damage to the structure being serviced by the water supply system and its surrounding environment. Since water supply systems are typically at least partially inaccessible (e.g., located behind structural walls or underground), it has been difficult to determine that a plumbing failure has occurred until significant damage has already been done. Moreover, relatively small leaks can go undetected for long periods of time since no significant damage may readily manifest itself. Such leaks result in considerable water wastage and may cause considerable expense to be incurred by the property owner for the increased water usage.
Numerous attempts have been made to devise mechanisms which detect leakage in a water supply system (see for example, U.S. Pat. No. 4,518,955, issued May 21, 1985 in the name of Meyer). The apparatus of this patent utilizes a fluid-flow pressure sensing device which detects a "no flow", "moderate flow", or "large flow" condition, and through a microcomputer activates a control device to operate an alarm and/or shut down the supply if the flow is determined to be a leak or plumbing failure. This particular sensing device is dependent upon unique pressure conditions associated with a specific water supply system. That is to say, without significant modifications to the device, if the pressure conditions change under normal operation (such as adding another take-off line for example), the device is no longer capable of giving a valid reading. Moreover, leak detection is based upon sensing flow above a certain preselected flow level. Such a method of predicting that a leak has occurred is severely limited and highly inaccurate due to the wide range of water usage to which any particular supply system is subjected. Specifically, the preselected flow level has to be high enough to accommodate a maximum permissible usage, and being at such a level may not be cabable of detecting a leak which is at a lesser flow level.